This invention relates to a method and apparatus to improve an attending physician's or anesthesiologist's knowledge regarding the patient's status during and after a surgical procedure, and, consequently decreasing the risks to the patient stemming from that procedure. Specifically, the invention involves an apparatus capable of providing immediate information regarding a patient's cumulative blood loss during and after transurethral resection of the prostate, also called transurethral prostatectomy. The invention is also useful in the measurement of blood loss during and following a nephroscopy or a balloon dilation of the prostate.
All male humans have a prostate gland located just below the bladder. The prostate surrounds the urethra and produces seminal fluid. At puberty, the prostate is approximately the size of a chestnut. In many men, the prostate begins increasing in size around the fifth decade and gradually may reach the size of a baseball or even larger. Frequently, this growth is benign, although at times it is cancerous.
As the prostate grows larger, it squeezes inwardly around the urethra, narrowing it, and at times eventually leading to urinary retention in the bladder and to other complications.
Symptomatic growth or hypertrophy of the prostate is in general treated by removal of the excessive tissue growth by a surgical procedure called a prostatectomy. When the size, shape, and position of the enlarged prostate permit, a surgical procedure known as a transurethral resection (TUR) of the prostate is preferred. A TUR does not require an external incision, entails less blood loss, has fewer associated complications, and permits a shorter recovery period than an open prostatectomy.
A transurethral resection of the prostate is accomplished using an instrument called a resectoscope which is inserted through the urethra and which permits the physician to see inside the patient's urinary tract and to cut excess tissue using an electric loop extending from the resectoscope. The surgeon removes the obstructing tissue a piece at a time, and bits of tissue and accompanying blood are flushed out with a sterile irrigant which may enter and exit through a tube of the resectoscope. The removed tissue, associated blood and the flushing fluid are drained by tubing from the barrel of the resectoscope to a drain in the floor of the operating room.
In most patients, the transurethral resection of the prostate is carried out while the patient is anesthetized by spinal or epidural anesthesia. In managing patients undergoing such anesthesia, it is extremely helpful and important to the anesthesiologist to accurately know how much blood the individual patient has lost. It is also important to monitor a patient's blood loss following a transurethral resection to avoid post-operative complications. Blood loss during and following a transurethral resection of the prostate may, in extreme cases, vary from about thirty (30) milliliters to nineteen-hundred (1900) milliliters, and commonly varies from two-hundred (200) to eight-hundred (800) milliliters. At the present time no practical means is generally available for the anesthesiologist to continuously monitor a given patient's blood loss, since the volume of blood is intermixed with the volume of flushing fluid and drained into a drain in the operating room floor.
Simple expedients such as noting the drop in the level of the bottle of flushing fluid which feeds into the resectoscope, collecting the drained fluid and then estimating the difference in the two volumes to determine the blood loss, are inaccurate because of the absorption of fluid through venous channels at the surgical site. These methods are also inadvisable due to the possibility of the facilitation of bacterial contamination when the blood and flushing fluid are collected in a receptacle rather than drained away.
U.S. Pat. No. 4,562,842 discloses measuring apparatus for monitoring the loss of blood during a surgical procedure. The apparatus measures volume and weight of repetitive samplings of the mixture of blood and flushing fluid and then calculates the loss of blood based on known densities of blood and flushing fluid. The apparatus requires a reservoir to hold the blood/flushing fluid mixture while the necessary measurements of volume and weight are performed on volumes of the mixture withdrawn intermittently from the reservoir.
U.S. Pat. No. 4,575,240 discloses an apparatus for the spectrophotometric analysis of blood samples. The apparatus of the '240 patent is constructed such that blood samples can be analyzed automatically, but not continuously.
U.S. Pat. No. 4,357,105 discloses a high accuracy portable hemoglobinometer. The hemoglobinometer disclosed in the '105 patent utilizes spectrophotometric principles to determine the concentration of hemoglobin in properly prepared blood samples. One drawback of the hemoglobinometer of the '105 patent is that the hemoglobinometer does not analyze samples on a continuous basis.
U.S. Pat. No. 4,227,814 discloses an optical density detector for sensing the change in optical density of a fluid flowing through a flexible and light transmitting tube. The detector disclosed in the '814 patent is capable of continuously monitoring a flowing liquid through a clear and flexible tube. However, the detector is only capable of an on/off type analysis. It detects only the presence or absence of red blood cells in plasma flowing through the tubing of the detector, not relative amounts of red blood in the flushing fluid.